Devices and methods for reducing vehicle drag

ABSTRACT

An apparatus for reducing the drag of a trailer is provided. The apparatus can further include a pair of fairings configured to be positioned on opposite sides of a trailer in front of wheels on the bottom of a trailer, a pair of fairings configured to be positioned on opposite sides of a trailer behind the wheels on the bottom of a trailer, with both pairs of fairings placed and shaped to direct the air smoothly around the wheels and tires and through the center of the trailer. The apparatus can also include a ramp in front of the suspension components, aerodynamically shaped wings on the axles, and a rear diffuser, such components configured to direct air smoothly between the trailer suspension and the ground. The directed high energy air from the apparatus results in a reduced trailer base drag.

BACKGROUND

An ongoing effort to reduce drag in vehicular structures is of greatimportance as fuel economy becomes an increasingly large considerationin vehicular design. As the drag of a vehicle increases, the amount offuel needed to move the vehicle also increases due to the greater energyrequired to overcome the drag. For instance, it has been stated that fora vehicle traveling at 70 mph, about 65% of the total fuel consumptionof the vehicle's engine is used to overcome drag. Therefore, even asmall reduction in the drag experienced by a vehicle traveling athighway speeds can result in a significant improvement in fuel economy.

For instance, heavy-duty vehicles such as tractor-trailers (also knownas semi tractors, tractors, class 8 long haul trucks, transfer trucks,18-wheelers, semis, etc.) have a tall and wide box-shaped profile thatcreates a significant amount of drag compared to smaller vehicles on theroad. For instance, Table I lists common drag coefficients of roadvehicles.

TABLE I Type of Vehicle Drag Coefficient (Cd) Low Drag Production Car.26 Typical Sedan  .3-.35 Sport Utility Vehicle .4-.5 Pick-up Truck.4-.5 Conventional Class 8 long haul tractor trailers .59-.63

In the U.S., vehicles commonly used to move freight typically include atractor which powers the vehicle and a trailer which contains thefreight. Tractors usually have 3 axles, the front, or “steer”, axlehaving two wheels, and two rear, or “drive”, axles each having a pair ofwheels on each side. The most common configuration of this type oftractor has 10 wheels; however, in some cases the traditional pairs ofwheels and tires are replaced by single wides; also known as “supersingles”, or wide-base singles. Single wide tires and wheels reduce theweight of the semi-trailer and in some cases reduce the rollingresistance of the vehicle. Tractors equipped with single wides only havesix tires and wheels. Smaller tractors, having a single drive axle (for6 wheels in total) are often used to pull shorter trailers in tighturban environments. The tires, wheels, axles, drive shaft,differentials, and other wheel components also create drag.

Cargo trailers have a similarly tall and wide box-shaped profile thatcreates drag because the enclosed cargo space of a trailer is oftenrectangular in shape. The most common type of cargo trailer in the U.S.is a dry box van that is 53 feet long. Most common cargo trailerstypically have two “tandem” axles at the rear, each of which has a pairof wheels for 8 wheels on the trailer. Tires and wheels on trailers canalso be replaced with single wides, reducing the total number of tiresand wheels on the trailer from 8 to 4. Again, the tires, wheels, axles,and other wheel components create drag. A cargo trailer also typicallyincludes landing gear, which includes legs that the trailer rests uponwhen detached from a tractor. The landing gear can also create drag.

Certain devices are known in the art, such as trailer sideskirts,fairings, trailer end caps, boat tails, and the like, which attempt toaddress certain areas of drag on a vehicle. However, many of thesedevices have significant limitations in their ability to reduce drag ortheir ability to be easily integrated into fleet operations. As aresult, a comprehensive solution for improving drag on a vehicle isstill needed.

Thus, a need exists for devices that are designed to provide dragreduction for a vehicle trailer. Methods relating to the utilization ofsuch devices would also be beneficial. Retrofit kits for incorporatingsuch devices into vehicles would also be beneficial.

SUMMARY

In accordance with certain embodiments of the present disclosure, avehicle trailer is provided. The trailer includes a roof and a floorseparated from each other by a pair of walls that extend along thelength of the floor. The roof has a front edge and a rear edge and thewalls have a height that extends from the floor to the front edge of theroof, the height being substantially the same along at least a portionof the length of the walls.

The vehicle trailer further comprises an apparatus for reducing the dragof the trailer through reduction in the size of the wake behind thetrailer, increasing the pressure in the wake, and reducing the drag ofthe wheel and suspension components underneath the trailer.

In accordance with certain embodiments of the present disclosure, theapparatus can include an aerodynamic rain gutter component having afront edge and rear edge which is positioned on the roof adjacent to therear edge of the roof such that the front edge of the rain guttercomponent contacts the roof and the rear edge of the rain guttercomponent does not contact the roof. The apparatus can further include apair of fairings configured to be positioned on opposite sides of atrailer in front of wheels on the bottom of a trailer, a pair offairings configured to be positioned on opposite sides of a trailerbehind the wheels on the bottom of a trailer, with both pairs offairings placed and shaped to direct the air smoothly around the wheelsand tires and through the center of the trailer. The apparatus can alsoinclude a ramp in front of the suspension components, aerodynamicallyshaped wings on the axles, and a rear diffuser, such componentsconfigured to direct air smoothly between the trailer suspension and theground. The directed high energy air from the apparatus results in areduced trailer base drag.

Other features and aspects of the present disclosure are discussed ingreater detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure, including the best mode thereof,directed to one of ordinary skill in the art, is set forth moreparticularly in the remainder of the specification, which makesreference to the appended figures in which:

FIGS. 1A and 1B illustrate a conventional tractor-trailer combination;

FIG. 1C illustrates a drag assessment of a conventional trailer.

FIGS. 2A and 2B illustrate perspective views of a trailer in accordancewith certain embodiments of the present disclosure;

FIG. 3A illustrates a perspective view of a trailer in accordance withcertain embodiments of the present disclosure;

FIG. 3B illustrates a plan view of a rain gutter component in accordancewith certain aspects of the present disclosure;

FIGS. 4A and 4B illustrate perspective views of a trailer in accordancewith certain embodiments of the present disclosure;

FIG. 5A illustrates a low pressure wake that forms at the rear of aconventional trailer when being pulled at highway speed;

FIG. 5B illustrates reduction in drag by directing the incoming air flowbetween the trailer wheel assemblies and injecting the high velocity airstream into the trailer wake at the rear of the trailer in accordancewith certain embodiments of the present disclosure;

FIG. 6 illustrates the drag contributions from the trailer back,underside, sides, and top and illustrates the reduction in drag fromthese trailer systems as a result of equipping the trailer with thecomponents of the present disclosure.

DETAILED DESCRIPTION

Reference now will be made in detail to various embodiments of thedisclosure, one or more examples of which are set forth below. Eachexample is provided by way of explanation of the disclosure, notlimitation of the disclosure. In fact, it will be apparent to thoseskilled in the art that various modifications and variations can be madein the present disclosure without departing from the scope or spirit ofthe disclosure. For instance, features illustrated or described as partof one embodiment, can be used on another embodiment to yield a stillfurther embodiment. Thus, it is intended that the present disclosurecovers such modifications and variations as come within the scope of theappended claims and their equivalents.

The present disclosure is generally directed to devices and methods forreducing vehicle drag caused by vehicle trailers. In this regard, theterm vehicle can refer to any type of vehicle. In particular, however,the present disclosure specifically contemplates use with heavy trucks,such as tractors and trailers connected thereto. The present disclosureidentifies key areas in which modifications to conventional trailers canresult in great reductions in vehicle drag, which can translate intoimproved fuel economy, reduced emissions of carbon dioxide, as well asother improved efficiencies.

As used herein, drag (also referred to as air resistance or fluidresistance) refers to forces that oppose the relative motion of anobject through a fluid (a liquid or gas). Drag forces act in a directionopposite to the velocity of the vehicle. Unlike other resistive forcessuch as dry friction, which is nearly independent of velocity,aerodynamic drag forces are dependent on the square of the velocity. Fora solid object moving through a fluid, the drag is the component of thenet aerodynamic or hydrodynamic force acting opposite to the directionof the movement. Therefore drag opposes the motion of the object, and ina powered vehicle it is overcome by thrust provided by the enginethrough the vehicle's drive train.

Turning to FIGS. 1A and 1B, a conventional tractor with sleepercompartment 10 with trailer 12 is illustrated. FIG. 1A is a side view ofthe tractor 10 with trailer 12 and FIG. 1B illustrates the underside. Aconventional tractor with sleeper 10 is shown as opposed to cab overengine design, which is also contemplated as a type of vehicle that canbe used with the present disclosure. A standard 53 foot long dry box vantrailer is illustrated but trailers of any length are contemplated foruse with the present disclosure

Tractor 10 includes side mirrors 14, axles 16, drive shaft 18, andwheels 20. Tractor also includes air dam 22. Trailer 12 is joined tosemi-trailer truck 10 at coupling point 24 typically referred to as the5^(th) wheel. Trailer 12 includes an enclosed cargo space 26. Enclosedcargo space 26 is generally rectangular in shape. Trailer 12 alsoincludes landing gear 28, axles 16, wheels 20, and suspension 29.

As discussed previously, many of the above-described components createdrag during operation of the vehicle. FIG. 1C illustrates a dragassessment of a standard dry van trailer. The trailer back isresponsible for creating the largest amount of drag on the vehicle. Thisis due to a low pressure wake that forms at the rear of the trailer whenbeing pulled at highway speeds. The low pressure wake is formed becauseair behind the trailer is moving at a very low speed relative to thehighway speed of the traveling vehicle. This low pressure wake pulls thevehicle back, creating the significant drag force. FIG. 5A shows animage of a low pressure wake that has formed at the rear of aconventional trailer being pulled at 65 miles per hour. In addition tothe trailer back, the trailer underside and tires also create asignificant amount of drag as the air collides with the tires, axles,and other fixtures underneath the trailer. The top and side surfaces ofthe trailer also create drag, although the drag is a relatively smallamount compared to the back and underside/tires.

In accordance with the present disclosure, certain improvements aredescribed which can significantly reduce vehicle drag.

Referring to FIGS. 2A and 2B, perspective views of a trailer inaccordance with the present disclosure are illustrated. The illustratedtrailer 12 can be joined to a tractor (not shown).

Trailer 12 includes roof 30, two side walls 32, two edge walls 34, andfloor 36, which define a space 26 for transport of cargo. Roof 30includes a front edge 38 (oriented toward the front of the trailer),rear edge 40 (oriented toward the rear of the trailer), and two sideedges 42 (extending along the sides of the trailer). Each edge isgenerally straight. Side walls 32 separate roof 30 from floor 36 andextend along the length of floor 36. As shown in FIG. 2A, side walls 32have a height that is substantially uniform across the length of eachwall 32 except toward the rear edge 40 of trailer, where the height ofeach wall varies as described further herein. The height for a portionof each wall extends from floor 36 to the height of the front edge 38 ofroof 30 again, except toward the rear edge 40 of trailer, where, incertain embodiments, the height can increase and then decrease inconformity to the sloped surface of rain gutter component 44 (describedfurther below) adjacent thereto. Edge walls 34 face the front of thetrailer and rear of the trailer. Rear edge wall 34 can provide accessinto space 26 as will be described in more detail.

In accordance with the present disclosure, aerodynamic rain guttercomponent 44 is illustrated. Rain gutter component 44 can be positionedadjacent to rear edge 40 of roof 30, over the existing rain gutter onthe trailer and be configured so as to have a portion 44A that anglesaway from floor and a portion 44B that angles back towards floor topoints above and below the plane defined by the roof 30. Rain guttercomponent 44 has a curved, sloping surface. In certain embodiments, sidewalls of rain gutter component 44 similarly increase in height anddecrease in height in conformity with the slope, which results in aportion of each side wall 45 extending above the height of roof 30. Wheninstalled, rear edge 44C of rain gutter component has a lower distanceto the ground and/or floor 36 than front edge of roof 38 and/or the sidewalls 45 (if present) adjacent to rear edge except for the portion ofeach side wall (if present) immediately adjacent to rear edge 44C, suchportion (if present) having a substantially identical distance to groundand/or floor 36 with rear edge 44C. For instance, when the rain guttercomponent is installed, the distance between rear edge 44C and floor 36can be from about 100 inches to about 105 inches. The length of raingutter component 44 that is curved can vary. The length of rain guttercomponent 44 can be from about 16 inches to about 40 inches (bycomparison, in certain embodiments, the total length of roof 30 on astandard 53 foot dry van trailer can be about 636 inches). Similarly,width of rain gutter component 44 that is angled can vary. The width ofrain gutter component 44 is typically the same width as the trailer andcan be from about 100 inches to about 102 inches (by comparison, incertain embodiments, the width of roof 30 can also be from about 100inches to about 102 inches). The height of aerodynamic rain guttercomponent 44 from the trailer roof 30 is about 1 inch to about 3 inches.Portion 44A can be angled at an angle from about 5 degrees to about 15degrees, more particularly at an angle of about 9 degrees to about 11degrees and portion 44B can be angled at an angle from about 10 degreesto about 20 degrees, more particularly at an angle of about 12 degreesto about 16 degrees. In some embodiments, rain gutter component 44 issubstantially a curved panel. The thickness of such a rain guttercomponent 44 can be from about ⅛ inch to about ¼ inch.

In certain embodiments, additional flap 47 can extend from rear edge 44Cand rain gutter component 44 and can articulate between variousdifferent angles. For example, when installed, flap 47 continues thecurve shown in FIGS. 3A and 3B but can be co-planar with rear edge wall34 in a first mode, and then pivot into a second mode in which flap 47continues along the angle of portion 44B in the direction of the ground.It is contemplated that at times, access to space 26 results in flap 47being adjusted or flexed accordingly. For instance, flap 47 can be splitin two haves along the center to correspond with the doors that formrear edge wall 34. In such embodiments, flap 47 would be generally flushwith rear edge wall 34 when space 26 is being accessed by opening suchdoors. To provide needed flexibility, flap 47 can be made of flexiblematerial as would be understood by one of ordinary skill in the art. Forinstance, rubber or the like can be utilized for flap 47.

Flap 47 can have a length from about 6 inches to about 15 inches and awidth from about 100 inches to about 102 inches. Further, flap 47 canhave a thickness from about ⅛ inch to about ¼ inch.

Referring to FIGS. 3A and 3B, a flap 47 in accordance with the presentdisclosure is illustrated. In such embodiments, flap 47 extends beyondrear edge wall 34 such that the total length of roof 30 and flap 47 isgreater than the length of floor 36. For instance, flap 47 can extendfrom about 4 inches to about 10 inches past rear edge wall 34.

As discussed above, rear edge wall 34 can provide access into space 26as would be understood by one of ordinary skill in the art. One suchembodiment is illustrated in FIG. 2A. For example, if flap 47 is capableof articulating, rear edge wall 34 can include a component that canpermit adjustment across certain angles. In addition, rear edge wall 34can be a conventional sliding door or conventional swing doors as arefound on conventional trailers, with the size adjusted to accommodatethe rain gutter component 44 and/or flap 47.

In accordance with the present disclosure, certain other aspects aredescribed. For instance, fairings can reduce the drag of the trailer asa result of certain trailer components.

Turning again to FIG. 2B, another pair of fairings is illustrated. Thepair of components 58 is positioned in front of wheels 20 and/or wheelassemblies 20. In this regard, a wheel assembly includes any combinationof wheels, tires, axles, differentials, and other wheel-relatedstructure, such as struts, shocks, springs, control arms, brakecomponents, or the like. The components are configured to direct fluidflow between the pairs of wheels 20.

Referring to FIGS. 4A and 4B, each component 58 has a generallyparabolic shaped cross-section that is generally parallel to bottomsurface 36. For example, each component has a generally flat bottomsurface 59A and top surface 59B that are generally parallel to bottomsurface 36 with the bottom surface 59A and top surface 59B having agenerally straight edge 60 and a generally curved edge 61. The leadingportion 62 of component 58 is oriented toward the front of the trailer12 and the trailing portion 63 is oriented toward the rear of thetrailer 12 with the side portions 64 connecting the leading portion 62and trailing portion 63. The leading portion 62 is curved in conformitywith the parabolic shaped cross-section and curved edge 61. In addition,the leading portion 62 is curved as it extends from the bottom surface59A to the top surface 59B thereof. The trailing portion 63 curvesinward towards the front of trailer 12 as it extends from bottom surface59A to top surface 59B such that the trailing portion 63 is generallycomplimentary to the curve of one or more adjacent wheels 20.

Each component 58 can be generally identical and positioned, asdiscussed above, oriented on opposite sides of trailer in front of eachpair of wheels 20. Each component 58 can have a length from about 12inches to about 28 inches. In addition, each component can have a widthfrom about 16 inches to about 27 inches. Each component can have aheight from about 19 inches to about 42 inches. For instance, thelength, width, and height can be comparable to that of each pair ofwheels.

Turning again to FIG. 4A, sloped component 66 can be positioned in frontof wheel assemblies 58, with, in certain embodiments, at least a portionpositioned in between components 58. The sloped component 20 can haveone or more sloped surfaces 68 that slope from bottom surface 36 to agenerally flat surface 70. The leading portion 72 of sloped component isgenerally flush with bottom surface 36 of trailer with the surface 68 ofsloped component 66 sloping downward in the direction of the ground. Theangle of slope can be from about 15 degrees to about 33 degrees. Sideportions 76 of sloped component 66 are generally coplanar with trailerside walls 32.

Sloped component 66 can have a length from about 36 inches to about 114inches. In addition, sloped component 66 can have a width from about 30inches to about 68 inches. Sloped component 66 can have a height fromabout 16 inches to about 40 inches. For instance, the width can beconfigured so that at least a portion of sloped component 66 fits inbetween components 58.

Referring again to FIGS. 4A and 4B, sloped component 66 directs airflowunderneath one or more axle components 80, which may or may not beintegrally formed with sloped component 66. Axle component(s) 80 isconfigured to be placed over the axle 16 of trailer 12. Axlecomponent(s) 80 can be in the form of one or more axle wings that have acurved front portion 82 and a generally flat body 84. Axle component(s)80 can have a length from about 12 inches to about 36 inches. Inaddition, axle component(s) 80 can have a width from about 23 inches toabout 68 inches. Axle component(s) 80 can have a thickness from about ⅛inch to about ½ inch. For instance, the width can be configured so thatat least a portion of axle component(s) 80 fits in between wheels 20 ofone or both axles 16.

For instance, in certain embodiments, two axle component 80A and 80B canbe generally identical and positioned, as discussed above, oriented overthe axle of trailer in between each pair of wheels 20 such that slopedportion 82A of the rear axle component 80A is adjacent to the flat body84B of the forward axle component 80B.

Turning again to FIG. 4B, yet another pair of fairings is illustrated.The pair of rear components 90 is positioned in behind wheels 20 and/orwheel assemblies 20.

Referring to FIGS. 4A and 4B, each rear component 90 has a generallywedge shaped cross-section that is generally parallel to bottom surface36. For example, each component has a generally flat bottom surface 92Aand top surface 92B that are generally parallel to bottom surface 36with the bottom and top surfaces 92A and 92B having a generally straightedge 94 and a generally curved edge 96. The leading portion 98 of rearcomponent 90 is oriented toward the front of the trailer 12 and thetrailing portion 100 is oriented toward the rear of the trailer 12 withthe side portions 102 connecting the leading portion 98 and trailingportion 100. The leading portion 98 is curved generally complimentary tothe curve of one or more adjacent wheels 20. In addition, the leadingportion 98 is curved as it extends from the bottom surface 92A to thetop surface 92B thereof. The trailing portion 100 curves outward towardsthe rear of trailer 12 as it extends from bottom surface 92A to topsurface 92B.

Each rear component 90 can be generally identical and positioned, asdiscussed above, oriented on opposite sides of trailer in behind eachpair of wheels 20 such that they are in a mirror-image orientation. Eachrear component 90 can have a length from about 12 inches to about 30inches. In addition, each component can have a width from about 14inches to about 27 inches. Each component can have a height from about16 inches to about 36 inches. For instance, the length, width, andheight can be comparable to that of each pair of wheels.

As shown in FIGS. 2A and 2B, the present disclosure further includes adiffuser 110. The diffuser 110 can include an integrated bumper 112 orcan be placed around an existing bumper (as illustrated in FIG. 4B).Diffuser 110 can have a generally rectangular cross section and can bepositioned behind rear wheel assemblies 20 adjacent to the rear end oftrailer 12. The diffuser 110 can define a cut-out 111 of any suitableshape or size to enable the trailer to be positioned adjacent to aloading dock and/or attached to a loading dock. Diffuser 110 can includeone or more sloped surfaces 118 that slope from the center 114 towardsthe sides 116. The angle of slope can be from about 0 degrees to about26 degrees. As seen in FIG. 4B, diffuser 110 can be hollow and thediffuser can have an open face or can have a closed rear face making thediffuser a sealed cube like object.

Diffuser 110 can have a length from about 14 inches to about 98 inches.In addition, diffuser 110 can have a width from about 26 inches to about102 inches (the full width of the trailer). Diffuser 110 can have aheight from about 25 inches to about 42 inches. For instance, as withthe other components, the length, width, and height can be comparable tothat of each pair of wheels.

In this manner, the devices of the present disclosure reduce drag in anumber of ways including:

1. Directly minimizing the drag associated with incoming air flowcolliding with the tires, axles, brakes, and other mechanisms under thetrailer body. The sloped component 66, front wheel assemblies 20, andaxle wings 80A and 80B act as fairings to move the incoming air aroundthe tires, axles, brakes and other mechanisms under the trailer body.Additionally, this collection of components keeps the incoming air fromseparating as the air flows past the mechanisms underneath the trailer.

2. Accelerating and compressing the incoming air flow as it travelsbetween the collection of components (66, 58, 80A, 80B, 90, 110), thewheels, and the ground. The components, the wheels, and the groundcreate a tunnel with a rectangular cross section in which the compressedand accelerated air flows and ultimately is injected below the lowpressure wake at the rear of the trailer as shown in FIG. 5B (whencompared to a conventional trailer as illustrated in FIG. 5A). At therear of the trailer, the diffuser 110 deflects the air flow toward theground at an angle from 3 degrees to 10 degrees as shown in FIG. 5B.Injecting the accelerated and compressed air below the low pressure wakepulls the wake down and reduces its size, the sum of which increases thepressure in the wake, thereby reducing the resulting drag.

3. Directing the attached high velocity incoming air flow from the topof the trailer to the rear of the trailer at a downward angle ofapproximately 12-15 degrees as shown in FIG. 5B. The aerodynamic raingutter component 44 and flap 47 keeps the air flow attached and directsthe air downward into the low pressure wake. Injecting this highvelocity air flow into the low pressure wake reduces the size of thewake and adds energy to it. This increases the pressure in the wake,thereby reducing the resulting drag. FIGS. 5A and 5B compare the flowfield at the rear of the trailer without the components of the presentdisclosure to the flow field of the same trailer that is equipped withthe components of the present disclosure. FIG. 6 illustrates the dragcontributions from the trailer back, underside, sides, and top andillustrates the reduction in drag from these trailer systems as a resultof equipping the trailer with the components of the present disclosure.

It should be understood that while the present discussion and figuresdescribe a dual tire configuration, a single wide tire configuration isalso contemplated by the present disclosure. In such embodiments, thepresent disclosure can be modified as would be understood by one ofordinary skill in the art to achieve the improvements described herein.

All of the above-described elements can be formed from any suitablematerial as would be known and appreciated in the art. For instance,metals, plastics, or the like can be utilized. Unless otherwise stated,the elements can include a smooth outline to further reduce drag. Inaddition, it should be appreciated that any suitable mounting hardwareincluding common fasteners (such as nuts, bolts, or the like), latches,hooks, ties, adhesives, magnets, or the like, or any other conventionalsecuring methods as would be known in the art can be utilized inconnection with the present disclosure.

It should be understood and appreciated that various combinations of theabove described subject matter are contemplated by the presentdisclosure. In other words, drag improvements can be achieved by usingonly one of the above-described embodiments, but drag generally improvesif more than one component is utilized. In addition, the teachings ofthe present disclosure can be incorporated into new vehicle and trailermanufacture/sale as well as retrofit kits for upgrading existingvehicles and trailers.

The following examples are meant to illustrate the disclosure describedherein and are not intended to limit the scope of this disclosure.

EXAMPLES

Aerodynamic drag associated with trailers, tractor-trailer systems, andcomponents of the present disclosure were all assessed using NASA'sFully Unstructured Navier-Stokes 3D (FUN 3D) Computational FluidDynamics (CFD) model described further at http://fun3d.larc.nasa.gov. Inaddition, the actual fuel savings associated with trailers,tractor-trailer systems, and components of the present disclosure weredemonstrated using the industry standard Society of AutomotiveEngineer's (SAE) long-haul fuel-consumption test J1321 protocol,incorporated by reference herein, in a series of tests at theContinental tire proving grounds in Uvalde, Tex. The long-haulfuel-consumption test provides a standardized test procedure forcomparing the in-service fuel consumption of a test vehicle operatingunder two different conditions relative to the consumption of a controlvehicle.

Results of computational fluid dynamics modeling and simulations and SAEJ1321 testing are provided in Table IIA. In particular, Table IIA showsthat a modern tractor trailer combination equipped with the elements andcomponents described in the present disclosure has 10% less drag thanthe same tractor trailer without such components. For a tractor traileroperating on the highway at 65 miles per hour, a 10% reduction in dragresults in a 5.5% improvement in fuel efficiency.

As illustrated in Table IIB, the SAE J1321 protocol tests at theContinental tire proving grounds in Uvalde, Tex. demonstrated 6.81%improvement in fuel efficiency at 65 mph.

TABLE IIA Tractor Trailer Equipped with Baseline Tractor components ofthe Percent Trailer present disclosure Improvement Cd as calculated by.592 .5328 10% NASA's FUN 3-D Computational Fluid Dynamics Model Highwayfuel 6.25 miles per 6.587 miles per 5.4%  efficiency at 65 gallon gallonmiles per hour

TABLE IIB Demonstrated * Highway fuel 6.252 miles per 6.678 miles per6.81% efficiency at 65 mph gallon gallon Using SAE J1321 Protocol * Testat Continental Tire Proving Grounds in Uvalde, Texas, Apr.5^(th)-10^(th) 2010.

In the interests of brevity and conciseness, any ranges of values setforth in this specification are to be construed as written descriptionsupport for claims reciting any sub-ranges having endpoints which arewhole number values within the specified range in question. By way of ahypothetical illustrative example, a disclosure in this specification ofa range of 1-5 shall be considered to support claims to any of thefollowing sub-ranges: 1-4; 1-3; 1-2; 2-5; 2-4; 2-3; 3-5; 3-4; and 4-5.

These and other modifications and variations to the present disclosurecan be practiced by those of ordinary skill in the art, withoutdeparting from the spirit and scope of the present disclosure, which ismore particularly set forth in the appended claims. In addition, itshould be understood that aspects of the various embodiments can beinterchanged both in whole or in part. Furthermore, those of ordinaryskill in the art will appreciate that the foregoing description is byway of example only, and is not intended to limit the disclosure.

What is claimed is:
 1. A vehicle trailer, the vehicle trailer comprisinga roof and a floor separated from each other by a pair of opposing wallsthat extend at least partially along the length of the floor, the roof,floor, and walls defining a space accessible by a trailer door, the roofhaving a front edge and a rear edge, the vehicle trailer furthercomprising: a rain gutter component defining a sloped surface extendingbetween a leading edge and a trailing free edge, the rain guttercomponent being positioned adjacent to the roof such that a portion ofthe rain gutter component proximate to or including the leading edgecontacts the roof and the trailing free edge of the rain guttercomponent extends beyond the rear edge of the roof, the rain guttercomponent configured such that a distance of the sloped surface from theroof increases as the rain gutter component extends from the leadingedge across a first portion of the roof and then decreases as the raingutter extends towards the trailing free edge along a second portion ofthe roof, wherein the rain gutter component is non-movably attached tothe trailer such that the portion of the rain gutter componentcontacting the roof is maintained in a fixed position relative to theroof.
 2. The vehicle trailer of claim 1, further comprising a bottomfairing positioned on a bottom portion of the vehicle trailer, thebottom fairing being positioned forward of a rear edge of the vehicletrailer.
 3. The vehicle trailer of claim 1, wherein the rain guttercomponent is inclined at an angle from about 10 degrees to about 20degrees.
 4. The vehicle trailer of claim 1, wherein the rain guttercomponent is inclined downwardly at an angle from about 12 degrees toabout 16 degrees.
 5. The vehicle trailer of claim 1, wherein the raingutter component has a length from about 10 inches to about 40 inches.6. The vehicle trailer of claim 1, further comprising a diffuserconfigured to be positioned adjacent to a rear edge of the trailer,wherein the diffuser includes at least one sloped surface configured todirect airflow away from a center line of the trailer.
 7. The vehicletrailer of claim 6, wherein the diffuser further comprises a bumper. 8.The vehicle trailer of claim 7, wherein the bumper is integrally formedwith the diffuser.
 9. A kit for retrofitting an existing vehicletrailer, a roof and a floor separated from each other by a pair ofopposing walls that extend at least partially along the length of thefloor, the roof, floor, and walls defining a space accessible by atrailer door, the roof having a front edge and a rear edge, the kitcomprising: a rain gutter component defining a sloped surface extendingbetween a leading edge and a trailing free edge, the rain guttercomponent configured to be positioned adjacent to the roof such that aportion of the rain gutter component proximate to or including theleading edge contacts the roof and the trailing free edge of the raingutter component extends beyond the rear edge of the roof, the raingutter component configured such that a distance of the sloped surfacefrom the roof increases as the rain gutter component extends from theleading edge across a first portion of the roof and then decreases asthe rain gutter extends towards the trailing free edge along a secondportion of the roof, wherein the rain gutter component is configured tobe non-movably attached to the trailer such that the portion of the raingutter component contacting the roof is maintained in a fixed positionrelative to the roof.
 10. The kit for retrofitting an existing vehicletrailer of claim 9, further comprising: a bottom fairing configured tobe positioned on a bottom portion of the vehicle trailer, the bottomfairing being configured to be positioned forward of a rear edge of thevehicle trailer.
 11. The kit for retrofitting an existing vehicletrailer of claim 9, further comprising: a diffuser configured to bepositioned adjacent to a rear edge of the trailer, wherein the diffuserincludes at least one sloped surface configured to direct airflow awayfrom a center line of the trailer.
 12. A method of retrofitting avehicle trailer, a roof and a floor separated from each other by a pairof opposing walls that extend at least partially along the length of thefloor, the roof, floor, and walls defining a space accessible by atrailer door, the roof having a front edge and a rear edge, the methodcomprising: installing a rain gutter component on the vehicle trailer,the rain gutter component defining a sloped surface extending between aleading edge and a trailing free edge, the rain gutter componentconfigured to be positioned adjacent to the roof such that a portion ofthe rain gutter component proximate to or including the leading edgecontacts the roof and the trailing free edge of the rain guttercomponent extends beyond the rear edge of the roof, the rain guttercomponent configured such that a distance of the sloped surface from theroof increases as the rain gutter component extends from the leadingedge across a first portion of the roof and then decreases as the raingutter extends towards the trailing free edge along a second portion ofthe roof, wherein the rain gutter component is non-movably attached tothe trailer such that the portion of the rain gutter componentcontacting the roof is maintained in a fixed position relative to theroof.
 13. The method of claim 12, further comprising installing a bottomfairing on the vehicle trailer, the bottom fairing positioned on abottom portion of the vehicle trailer forward of a rear edge of thevehicle trailer.
 14. The method of claim 12, further comprisinginstalling a diffuser on the vehicle trailer, the diffuser positionedadjacent to a rear edge of the trailer, wherein the diffuser includes atleast one sloped surface configured to direct airflow away from a centerline of the trailer.